1. Field of the Invention
This invention relates to a phase controlling device for a camshaft driven from a crankshaft of an internal combustion engine.
2. Description of the Prior Art
Internal combustion engines undergo a variety of conditions in which it is desirous to adjust the opening and closing times of the intake and exhaust valves with respect to the phases of the piston stroke. For instance, in a piston operated internal combustion engine, it is desirous to have the intake valves open as soon as possible during low speeds, and during high speeds it is desirous to retard the valve openings with respect to the piston stroke such that the opening of the exhaust valve is later to provide a longer power stroke.
Certain devices have been devised to attempt to bring about the advantages of valve retardation during high engine speeds. One such device is disclosed in U.S. Pat. No. 3,945,221 issued on Mar. 23, 1976 to Miokovic. The Miokovic patent discloses a coaxially mounted driving shaft and camshaft with a set of toothed pivoting arms engaging a gear mounted at the end of the camshaft. The pivoting arms are pivotable about a pin and are moved by a lever which is connected to a sliding member splined on the driving shaft. Axial movement of the spline member about the driving shaft causes the toothed arms to pivot to change the relationship of the driving shaft with respect to the camshaft.
U.S. Pat. No. 3,888,216 issued on June 10, 1975 also to Miokovic discloses a second system for controlling the opening and closing of the intake and exhaust valves. The device has two rocker arms which engage each of two rotatable shafts having cams thereon which are driven by the crankshaft of the internal combustion engine. Each camshaft has spiral fins upon which gears are splined thereupon. The two gears mesh with each other. In addition, the gears are in engagement with a fork which axially moves the gears along the camshafts to change relative phases of one camshaft with respect to the other. The fork is actuated by a hydraulic piston type actuator.
Another hydraulic actuated timed controlled system is disclosed in U.S. Pat. No. 3,827,413 issued on Aug. 6, 1974 to Meachum. The Meachum patent discloses a parallel crankshaft and camshaft which are connected by a drivechain. The chain is trained around a sprocket operably splined about an inner race. A complementary outer race is fitted thereabout with axially extending grooves therein. The inner race has angular extending slots. Ball bearings are seated within the grooves and slots. A hydraulic system axially moves the inner race with respect to the outer race to angularly position the sprocket with respect to the camshaft. In this way the crankshaft and camshaft are phase controlled.
A speed sensitive timing device is disclosed in U.S. Pat. No. 3,401,572 issued to Bailey on Sept. 17, 1968 which operably connects a crankshaft to a camshaft which drives a fuel injection pump. The timing device has a vortex pump which is speed dependent. Operation of the pump causes a helical splined gear to axially move through an axially fixed gear against a force of a return spring axially biased between the gear and camshaft. The helical splines cause the camshaft to rotate as the gear axially moves. The gear is operably driven by the crankshaft. As the crankshaft increases speed, the pump forces the gear to axially move against the force of the return spring and retarding torque of the camshaft thereby rotating to advance the camshaft relative to the crankshaft.
A simple, economical and easily packaged timing device is needed that is independent of servo-mechanisms and hydraulics which can retard the timing of a camshaft with respect to a crankshaft.